Today the immediate danger has passed and Nikolayeva, 60, is more concerned about what to do with the emergency water cannisters that cost a third of her 100-dollar a month pension. "The authorities and television are to blame for sparking panic," she said.

But although chemicals released into China's Songhua River in a November factory explosion have largely dispersed or been diverted from Khabarovsk's 600,000 people, experts warn the Amur's real real problems are only building up.

The pollution scare was "the tip of the iceberg" in an ecosystem threatened by surging industrial activity in China and deep-seated environmental problems in Russia itself, Nikolai Efimov at the World Wildlife Fund in Russia's far eastern region said.

"For several years, tests of water taken from the Amur riverbed have shown increases in the presence of hydrocarbons, pesticides, including DDT, mercury, heavy metals, phosphorous" and other toxic substances, he said.

"Ecologists and scientists started talking about the sickness of the Amur River in 1997," he said. "That was when phenol levels were discovered to be massively too high -- 906 times above normal."

A big part of the blame lies on the rash of new factories built along Chinese waterways connecting to the Amur, he said.

Khabarovsk regional officials say that there are more than 60 potentially dangerous industrial sites along Chinese rivers connecting to the Amur. And while just 1.5 million Russians live in the Amur area, 70 million Chinese live just across the border, Khabarovsk regional officials say.

"Most drainage in major Chinese settlements is poorly filtered or simply poured into the river without any cleaning and it then flows into the Amur," Efimov said. "We are noticing a fall in the fish population. Every year ... colonies of bacteria are spreading."

German Novomodny, an ecologist at the Pacific Scientific Research Centre for Fisheries, agreed that the Amur faces a difficult future, but said that China is not necessarily to blame.

High phenol levels are a mark of many northern Russian rivers, he said, and are caused above all by insufficient water levels following a decade of low rainfall and the drawing down of the water by Russian and Chinese hydroelectric power stations.

"The Amur's level is significantly below what it should be and if there had plenty of water this year then no one would have been talking about a pollution threat to Khabarovsk -- the river would have dealt with that itself," Novomodny said.

Novomodny denied that fish stocks were falling due to pollution, saying that "not one species found in the Amur River is under threat of disappearing."

Instead, danger lurks around a less expected corner: the introduction into the river from China of non-native species.

"Most of these new species are fish that have escaped from fish farms in China. You even find tropical fish around Khabarovsk. That's the real danger to our local fish."

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